Lifting device for lifting metal sheets



May 6, 1969 J. F. ARCHER LIFTING DEVICE FOR LIFTING METAL SHEETS Filed Nov. 28, 1967 Sheet Je an Franc 01s ARCHER Inve nt or May 6; 1969 J. F. ARCHER LIFTING DEVICE FOR LIFTING METAL SHEETS Z ofS Sheet Filed Nov. 28, 1967 Jean Francois ARCHER Inventnr May 6, 1969 J. F. ARCHER LIFTING DEVICE FOR LIFTING METAL SHEETS Sheet Filed Nov. 28, 1967 Jean Franois ARCHER Invaptor United States Patent U.S. Cl. 294104 5 Claims ABSTRACT OF THE DISCLOSURE A plate-lifting device having a rotatable eccentric cam and an opposed arm or plate, both mounted on a body, with a chain part-way round the cam to rotate it, thus seizing one or more plates between the cam and the arm, with holes in the body or cam for insertion of a safety peg to lock the cam to the body when a plate is being lifted.

My present invention relates to a plate-lifting device.

Gripping devices are known, particularly for lifting metal sheets, comprising a pivoting clamping cam which is connected to the lifting hook of a crane by a flexible connection, such as a cable or a chain passing over a portion of the periphery of the cam.

As :a result of this arrangement, the device may have a considerable gripping range, i.e. it can grip either a single thin sheet, a stack of sheets, or a very thick sheet while exerting an adequate clamping force whatever the thickness of the sheet or assembly of sheets, since the clamping force is always proportional to the weight of the clamped article. However, it may happen in the course of a lifting operation that the gripping device may strike against an obstacle and cause the lifting cable or chain to go slack. The clamping force then becomes practically zero and the article may fall and cause an accident.

The present invention concerns an improvement in or relating to a gripping device of the above type, and the object thereof is to surmount this disadvantage.

According to the present invention, the clamping cam and/or the body of a device of the kind described are provided with a series of holes in which a safety peg can be inserted, permitting the locking of the cam. In a particularly advantageous embodiment, in which a small number of holes in the body permits the cam to be locked over the entire range of use of the device, the profile of the cam used for clamping is extended by an arc which is generally circular, but eccentric relative to the axis of the cam and is displaceable across the holes formed in the body and serving for the passage of the safety peg, the holes being disposed in an arc of a circle which is substantially co-axial with the pivot of the cam, and having a radius approximately equal to that of the arc of the cam used for locking.

To permit the gripping device to slide easily under an assembly of sheets, the device may include two side plates between which the clamping cam is mounted pivotally, and which are connected together by a flat clamping arm disposed opposite to the cam and perpendicular to the side plates.

Assembly of the locking arm to the side plates may be assisted by gussets disposed externally of the side plates, the locking arm projecting laterally relatively to the gussets. The arm thus presents unwelded portions between the gussets and beyond them in which the metal has not been modified by welding and which portions thus elfectively resist stress.

Two embodiments of a metal sheet lifting device according to the present invention are described hereinafter, by way of example with reference to the accompanying drawing in which:

FIG. 1 is an elevation of the sheet-lifting device according to first embodiment of my invention;

FIG. 2 is an end view thereof;

FIG. 3 is a section of a detail taken on the line IIIIII of FIG 1; and

FIG. 4 is an elevation of the lower part of the device, as a second embodiment.

As shown in the drawing, the lifting device comprises two side plates 18 between which a clamping cam 4 is mounted pivotally. These two side plates are connected together by two cross pieces 2 and 3, the second of which acts as a shaft supporting cam 4, and by a flat arm 19 disposed opposite the cam 4, the inner face of which is provided with ridges 20. The first link 16aof a link chain 16 is welded to the periphery of the cam 4, the chain then passing over a grooved wheel 21 mounted to pivot on the cross piece 2. When traction is exerted on the chain upwardly, the latter tends to pivot the cam 4 in a direction to make its periphery approach the arm 19 (counterclockwise in FIG. 1).

Assembly of the arm 19 to the side plates 18 is assisted by welded gussets 22 disposed externally of the side plates. The arm 19 is sufliciently wide to project substantially beyond the side plates, as shown at 19a.

In its portion extending between the side plates 18, the chain is of a particular type: those of its links which are perpendicular to the side plates are kept separate from one another by grooved discs 23, each disc having a radius substantially equal to the outer radius of the link and the minimum cross section of each disc having a diameter substantially equal to the space between two adjacent links when the chain is stretched. The grooved discs prevent the chain from tangling and, consequently, jamming between the side plates 18.

The side plates 18 are pierced with a series of holes 24 in one or another of which a tapered safety peg 25 may be introduced to lock the cam 4. As may be seen from the drawing, these holes are disposed so that they can be traversed in succession by the profile of the cam when it pivots and approaches the arm 19, the hole 24 in which the peg is inserted being selected according to the position of the cam. In view of the great gripping capacity of the lifting device, it may be dangerous to insert the peg holes provided in the side plates without the risk of dangerously weakening them; therefore, I provide holes 26 in the cam 4, which holes may then appear on the outside of the side plates, a feature which makes it possible to insert in them the peg 25 which abuts the edges of the side plates.

In FIG. 4 the two side plates 18 are shown; between these plates the clamping cam 4 is mounted to pivot at 3 opposite and the arm 19 with which the cam 4 co-operates.

The cam 4 has a profile 4a which is used for clamping packages. The profile is extended by an arc 4b displaceable in front of the holes 24 provided in the side plates 18 for the passage of a safety peg.

The arc 4b is substantially circular, but its center 26 is not on the axis 3; in this embodiment the arc is eccentric relative to this axis on the connecting radius of the arc 4a and 4b.

The holes 24, which are four in number in this case, are disposed in an arc of a circle 27, the radius of which is approximately equal to the radius of the arc 4b, and the centre of which is at 3.

FIG. 4 shows that when the cam 4 pivots, the arc 4b sweeps in succession over the various holes 24 and that these holes, while fewer in number than in the previous case and thus not substantially weakening the resistance of the side plates 18, permits the insertion of a lockingpeg both when the cam is in the maximum withdrawn position, shown in the drawings, and when it is practically in contact with the arm 19 or when it occupies any intermediate position. 7

I claim:

1. A lifting device for lifting metal sheets, said device comprising a body, a clamping cam pivoted on said body, a flexible coupling passing round a portion of the periphery of said cam for attachment to a lifting hook, said body being provided with a series of holes, and a safety peg insertable in one of said holes to lock said cam to said body, the profile of said cam being in the form of an are which is substantially circular but eccentric relative to the pivotal axis of said cam, said cam being displaceable with reference to said holes in said body wherein said holes are located along an arc of a circle which is substantially co-axial with the axis of said cam, said are of said circle having a radius approximately equal to that of the arc of said cam.

2. A lifting device as defined in claim 1, having two side plates forming said body between which plates said clamping cam is mounted, and a flat clamping arm disposed opposite said cam and connecting said plates together.

3. A lifting device as defined in claim 2, further comprising reinforcing gussets connecting said slide plates to said arm disposed externally of said side plates, the clamping arm projecting laterally beyond said gussets.

4. A lifting device as defined in claim 2 wherein said flexible coupling is a link chain, the edgewise-disposed links between the side plates being kept separate from one another by grooved discs, the meridian line of each of said discs having a radius substantially equal to the outer radius of said links and the minimum cross section of said discs having a diameter substantially equal to the space between two adjacent links.

5. A lifting device for lifting metal sheets, said device comprising a body; a clamping cam pivoted on said body; a link chain passing around a portion of the periphery of said cam for attachment to a lifting mechanism, said body being provided with a series of holes; a safety peg insertable in a selected one of said holes for locking said cam to said body, said body being formed with two side plates between which said cam is mounted and a flat clamping arm disposed opposite said cam and connecting said plates together; and grooved discs holding the edgewise-disposed links of said chain between said side plates separate from one another, the meridian line of each of said discs having a radius substantially equal to the outer radius of said links and the minimum cross section of said discs having a diameter substantially equal to the spacing between two adjacent links.

References Cited UNITED STATES PATENTS 3,150,895 9/1964 Lebre 294-101 3,178,219 4/1965 Renfroe 294--104 3,318,630 5/1967 Bryant 294-104 FOREIGN PATENTS 79,540 11/ 1962 France.

ANDRES H. NIELSEN, Primary Examiner. 

